Dual Magnetic Sensor Angular Position Detection
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Solution Overview
Problem
Existing angular position sensing systems using magnetic field sensors face errors due to non-straight magnetic field lines and manufacturing inaccuracies, leading to position tolerances and sensitivity to external magnetic fields.
Innovation Solution
A ring magnet with an axis of rotation and an annulus is used, with two magnetic sensors positioned one within and one outside the annulus to measure magnetic field lines, providing differential measurements that reduce angle errors and are less susceptible to external fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single magnetic sensor is positioned to measure magnetic field lines from a ring magnet, then the sensor can detect angular position changes, but angle errors occur due to non-straight magnetic field lines and sensor position tolerances
Solution Approach 1:
The patent divides the sensing function into multiple sensors positioned at different locations (within the annulus and outside the annulus). By segmenting the measurement task across multiple sensors, the system can average their readings to cancel out position-dependent angle errors, thereby improving overall measurement precision despite manufacturing tolerances
Solution Approach 2:
The patent changes the spatial parameter of sensor positioning by placing sensors at specific radial distances from the magnet (one within the annulus at distance greater than inner radius and less than outer radius, another outside the annulus). This parameter optimization ensures that magnetic field lines cross the sensors at consistent angles, reducing angle errors while accounting for position tolerances
2Measurement precision
If a magnetic sensor is positioned close to the ring magnet to improve signal strength, then measurement sensitivity increases, but the sensor becomes more sensitive to external magnetic fields
Solution Approach 1:
The patent uses multiple sensors to provide redundant measurements that can be processed to distinguish between the magnetic field from the ring magnet and external magnetic fields. By comparing readings from sensors at different positions, the system can identify and compensate for external field interference, maintaining sensitivity while reducing vulnerability to harmful factors
Solution Approach 2:
By using multiple sensors positioned at different locations, the patent segments the measurement function so that external magnetic fields affecting all sensors similarly can be identified and cancelled through differential measurement or averaging, thereby maintaining signal sensitivity while reducing external field interference
3Measurement precision
If the sensor reading radius is optimized to minimize angle error, then measurement accuracy improves, but the system becomes more sensitive to sensor misplacement due to position tolerances
Solution Approach 1:
The patent employs multiple sensors at different radial positions rather than relying on a single optimal position. This segmentation approach ensures that even if individual sensors are misplaced within tolerance ranges, the overall measurement remains accurate because the sensors are positioned such that field lines cross them at consistent angles, and their readings can be averaged to cancel errors
Solution Approach 2:
The patent anticipates potential sensor misplacement by positioning sensors within a range (within annulus and outside annulus) where the magnetic field geometry naturally compensates for position variations. This beforehand cushioning through strategic positioning ensures that angle errors remain minimized even with manufacturing tolerances
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration achieves high accuracy in angular position detection by averaging the measurements from the two sensors, minimizing errors caused by positioning inaccuracies and external magnetic fields, while maintaining precision even with slight sensor misplacement.
Implementation Method 1
A magnetic field sensor, such as a Giant Magnetoresistive sensor (GMR), Anisotropic Magnetoresistance (AMR) sensor, Hall-sensor, etc. is positioned so as to sense changes in the magnetic field generated by the magnet
Implementation Method 2
A magnetic field sensor, such as a Giant Magnetoresistive sensor (GMR)
Implementation Method 3
Anisotropic Magnetoresistance (AMR) sensor
Implementation Method 4
Hall-sensor
Data Source
AI summary
An angle sensor includes a ring magnet adapted to be attached to a rotatable shaft. The ring magnet has an axis of rotation and an inner radius and an outer radius extending from the axis of rotation to define an annulus. A first magnetic sensor is situated proximate the ring magnet to measure magnetic field lines within the annulus, and a second magnetic sensor is situated proximate the ring magnet to measure magnetic field lines outside the annulus.